Electrical device

ABSTRACT

The present invention relates to an electrical device, which includes two housing parts that can be joined to form one closed housing, the housing parts in the joined state enclosing a housing interior space, as well as an electrical/electronic circuit element arranged in the housing inner space, and a sealing material for protecting the circuit element. It is proposed that the two housing parts be configured as half-shells and the interior area of the half-shells, in each case, be subdivided by interior walls into at least two chambers, of which, in each case, a first chamber is filled with the sealing material and has spatial dimensions which are greater than the dimensions of the circuit element, the interior walls of the second half-shell, in the joined state of the two half-shells, overlapping the interior walls of the first half-shell with clearance, the interior walls of the first half-shell penetrating somewhat into the first chamber of the second half-shell, and the circuit element between the two half-shells being enveloped by the sealing material contained in the two first chambers, up to its electrical connections.

BACKGROUND INFORMATION

[0001] The present invention relates to an electrical device having the features cited in the preamble of claim 1.

[0002] From European Patent 0722 624 B1, an electrical device is known which has a first and a second housing part, which together form a closed housing. Arranged in the housing is a circuit element that is configured as a printed-circuit board, supporting elements configured in the first housing part penetrating through openings in the printed-circuit board. The support elements are configured so that the printed-circuit board moves in the direction of the first housing part when the second housing part is mounted, and a sealing material, arranged between the printed-circuit board and the first housing part, is subjected to compression and is squeezed into a position in which it forms a circumferential bulge on the side walls of the housing and as a result seals the contact area of the two housing parts. In the housing part that is sealed in this manner, a hollow space filled with air remains between the printed-circuit board and the second housing part. Retaining elements that are configured on the second housing part prevent the printed-circuit board, once it has arrived in its final position, from being pressed back into the hollow space by the compressive force of the compressed sealing material, as a result of which the sealing bulge would be pulled away from the housing walls. One disadvantage in the known device is that the printed-circuit board must be provided with openings for the supporting elements, and therefore space is lost on the printed-circuit board for the arrangement of electrical and/or electronic components. In addition, electrical connecting leads cannot be fed into the housing interior through the bulge-like seal between the housing parts, and therefore must be fed, in a cumbersome manner, through a separate passage in one of the two housing parts into the housing interior. This passage also must be sealed off, requiring additional expense. Harmful gases in the enclosed hollow space above the printed-circuit board can impair the mode of functioning of the electronic components on the printed-circuit board.

ADVANTAGES OF THE INVENTION

[0003] As a result of the electrical device according to the present invention having the features of claim 1, the disadvantages that arise in the related art are avoided, and reliable protection from harmful environmental influences is made possible for a circuit element arranged in a housing. The device assures a sufficient seal of the circuit element with respect to spray water, humidity, or submersion in water. The device is both simple as well as economical to manufacture and has two half-shells, whose interior area in each case is subdivided by interior walls into at least two chambers, of which a first chamber is filled with sealing material, preferably a gel, and has spatial dimensions that are larger than the dimensions of the circuit element. In the joined state of the two half-shells, the interior walls of the second half-shell overlap, with clearance, the inner walls of the first half-shell, as a result of which it is achieved that the sealing material contained in the two half-shells comes into contact around the circuit element in a frame-like, circumferential area, merges together, and thus seals off the circuit element circumferentially. Due to tolerances in the housing dimensions, tolerances in the pouring of the sealing material, and a shrinking process in response to the hardening of the sealing material, the sealing material poured into the first chambers before the assembly of the two half-shells forms a meniscus, so that the surface of the sealing material in the two chambers is curved in a concave manner and contacts the upper edges of the inner walls, although in the center of the chamber it recedes somewhat towards the interior. This cannot be avoided in a simple manner and, without taking countermeasures, results in hollow spaces arising above and below the printed-circuit board when the two half-shells are joined together, due to the concave curvature. In order, when the two half-shells are joined together, to prevent a faulty seal of the edge area of the printed-circuit board from arising as a result of an insufficient pressure of the sealing material in the edge area of the printed-circuit board, resulting from the presence of the hollow spaces, it is provided that the interior walls of the first half-shell, when the two half-shells are joined, penetrate somewhat into the first chamber of the second half-shell. As a result, it is achieved that the first chambers of the half-shells, engaging one another, form an overlapping area, a sufficient quantity of sealing material being pressed out of the overlapping area when the half-shells are joined in order that the edge area of the circuit element be enveloped in sealing material circumferentially in a sufficiently reliable manner. In this way, it is advantageously achieved that the circuit element between the two half-shells is encased up to its electrical leads by the sealing material contained in the two first chambers, i.e., it is arranged so as to be encapsulated in the sealing material.

[0004] Advantageous embodiments and refinements of the present invention are made possible by the features contained in the subclaims.

[0005] Advantageously, the interior area of each half-shell is subdivided, by two interior walls, running parallel to each other, which join to each other two side walls of the half-shells facing each other, into a first chamber arranged centrally and two second chambers laterally adjoining the first chamber. The second chambers provided in each half-shell function, inter alia, as the receiving areas for excess sealing material that is squeezed out of the first chambers when the two half-shells are joined together. As a result of the distance between the interior walls of the first and the second half-shells, a drainage channel is formed for the sealing material that is squeezed out of the first chambers, which is able to escape via the drainage channel into the second chambers.

[0006] The half-shells can be joined to each other advantageously using detention means. When the two half-shells are joined together, larger quantities of sealing material are compressed and are squeezed out of the overlapping area of the first chambers. Without a joining means, the strong compressive forces resulting from the compression would force the two half-shells apart. The detention means must therefore be able to withstand larger forces. It is therefore advantageous if the detention means, arranged on one half-shell, include detent hooks having barbed-shaped latches, the hooks, in each case, engaging in a guide slot arranged on the other half-shell and which, in each case, gripping from behind, using their latches, a projecting part arranged in the guide slot. The guide slots protect the latches, so that an unintentional unlatching of the latches is not possible. In particular, the width of each guide slot and the geometrical dimensions of the corresponding latches can be adjusted to each other, so that a latch engaging in a barbed-like manner behind the projecting part can no longer be detached from its latched position without being destroyed.

[0007] Advantageously, the side walls of the half-shells have cutouts, which in the joined state of the housing part form openings between the two half-shells for the feeding through of the electrical connecting leads. When the two half-shells are joined, the connecting leads running through the openings to the outside are embedded in the sealing material.

[0008] It is also advantageous to provide a strain relief device on at least one half-shell for the electrical connecting leads.

DRAWINGS

[0009] One exemplary embodiment of the present invention is depicted in the drawings and is discussed in the following description.

[0010] The following are the contents:

[0011]FIG. 1 depicts a cross section of an electrical device according to the present invention,

[0012]FIG. 2 depicts an enlarged segment from FIG. 1,

[0013]FIG. 3 depicts the second half-shell in a perspective representation,

[0014]FIG. 4 depicts the first half-shell in a perspective representation,

[0015]FIG. 5 depicts a top view of the first half-shell without the second half-shell, having a circuit element placed onto the sealing material, and a foil conductor connected thereto.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

[0016]FIG. 1 depicts an electrical device for a system for occupant classification in a motor vehicle. The device includes a housing 1, in which is arranged an electronic circuit element 4, for example, a printed-circuit board having electrical and/or electronic components 7, 8 arranged thereon. The printed-circuit board is connected via a foil conductor 6 to an undepicted seat mat for a vehicle seat, the seat mat having a plurality of local pressure-sensitive sensors. In addition, a wire 5 is provided, which connects the electronic circuitry arranged on the printed-circuit board to an airbag. The device makes it possible to determine the passenger occupancy of a vehicle seat and the type of passenger (child or adult) and, as a function of the data ascertained in this manner, to drive an airbag. The present invention, however, is not limited in principle to the exemplary embodiment depicted here but can also be used in other electrical devices which employ a circuit element that is arranged in the interior of a housing and that must be protected against environmental influences, such as humidity or harmful gases.

[0017] As is depicted in FIG. 1, housing 1 includes a first half-shell 2 and a second half-shell 3. Both are made of plastic and contain, in the joined state, a housing interior space, in which printed-circuit board 4 is arranged. The half-shells, however, can also be made of a different suitable material, for example, metal. A perspective representation of the interior area of the first half-shell is depicted in FIG. 4, and a representation of the interior area of the second half-shell is depicted in FIG. 3. As can be seen in FIG. 4, first half-shell 2 has four side walls 21, 22, 23, 24, and a base wall, on whose interior side a grating made of bars 41 is configured. Side walls 22 and 24, opposite each other, are linked to each other by two parallel interior walls 25, 26, which subdivide the interior area of first half-shell 2 into a first chamber 20 and two second chambers 27 a and 27 b, laterally adjoining. Essentially rectangular first chamber 20 is bordered by side walls 22 and 24 and interior walls 25 and 26. In addition, side wall 23 has a U-shaped cutout 29, and side wall 21 has a C-shaped cutout 28. On each of the two side walls, 23, two detent hooks 44 are configured, which, parallel to side walls 21, 23, protrude from the upper edge of the side walls. In second chamber 27 b, arranged adjoining to cutout 29, two pegs 42 and 43 protrude into the interior area from the base of first half-shell 2, the pegs functioning as a strain relief device for a foil conductor 6. In addition, the exterior edge of side walls 31, 32, 33, 34 has a partially circumferential rib 60.

[0018] Second half-shell 3 is depicted in FIG. 3 and is designed similarly to first half-shell 2. It has four side walls 31, 32, 33, 34, and a base wall, on whose interior side bars 51 are arranged in a grating-like manner. Side walls 32 and 34 are linked to each other by two interior walls 35 and 36, running parallel to each other. Side walls 32 and 34 and interior walls 35 and 36 border a centrally arranged first chamber 30, which is separated by interior walls 35 and 36 from two second chambers 37 a and 37 b, laterally adjoining. Side wall 33 has a U-shaped cutout 39, and side wall 31 has a C-shaped cutout 38. In addition, four through guide slots 54, having a rectangular cross section, are introduced into side walls 31 and 33 for detent hooks 44 of first half-shell 2. Guide slots 54 extend parallel to side walls 31, 33 and have at their ends in each case an opening 57, 58 (FIG. 2). The exterior edge of side walls 21, 22, 23, 24 is provided with a partially circumferential groove 61, into which rib 60 of second half-shell 3 engages when the two half-shells are joined together.

[0019] The length and width of first chamber 20 of first half-shell 2 and the length and width of first chamber 30 of second half-shell 3 are in each case dimensioned larger than the length and width of printed-circuit board 4. The distance between interior walls 35 and 36 of second half-shell 3 is dimensioned larger than the distance between interior walls 25 and 26 of first half-shell 2.

[0020] When the device is manufactured, first, both first chambers 20 and 30 are filled to the upper edge of the bordering interior walls and side walls with a fluid sealing material that is not depicted in FIG. 3 and FIG. 4. The highly viscous sealing material is made of, for example, a hardened gel. The gel can have a composition as is depicted in European Patent 0 722 624 B1. The gel, poured into chambers 20, 30, forms a surface that has a concave curvature, the surface receding to the inside in the central area of the first chambers, towards the chamber base. Subsequently, as is depicted in FIG. 5, a printed-circuit board 4, which is provided with electrical and/or electronic components 7, 8, is placed onto gel filling 12 of first chamber 29 of the first half-shell. Printed-circuit board 4 is joined to a foil conductor 6 of the seat mat. Foil conductor 6 has two layers of contact strips 6 a and 6 b, insulated from each other, which in the end area are separated and are connected to corresponding contact surfaces on the upper side and the lower side of circuit board 4, as can be seen best in FIG. 2. As is depicted also in FIG. 5, wire conductors 15 of a connecting cable 5 are electrically connected to a connector 8 on printed-circuit board 4 for driving an airbag. Cable conductors 15 can be arranged in second chamber 27 a of first half-shell. Foil conductor 6 has circular cutouts, through which pegs 42 and 43 penetrate, as a result of which a strain relief device is formed for foil conductor 6. As can be seen very well in FIG. 5, the edge of printed-circuit board 4 is separated from side walls 24 and 22 by a distance b of some millimeters and is separated from interior walls 25 and 26 by a distance a, also of some millimeters.

[0021] Subsequently, second half-shell 3 is placed onto first half-shell 2. In this context, four detent hooks 44 of first half-shell 2 penetrate through openings 57 into guide slots 54 of second half-shell 3, as can best be seen in FIG. 2. Because the distance between interior walls 35 and 36 of second half-shell 3 is dimensioned larger than the distance between interior walls 25 and 26 of first half-shell 2, interior walls 35 and 36 of second half-shell 3, in this context, lie beyond interior walls 25 and 26 of first half-shell 2 by a distance d. When both half-shells 2, 3 are brought into closer proximity, gel layers 12 and 13 in both first chambers 20 and 30 come into contact in the edge area of printed-circuit board 4. As a result of further pressure, it is achieved that interior walls 25, 26 of the first half-shell penetrate into first chamber 30 of second half-shell 3 a certain distance c.

[0022] Advantageously, interior walls 25, 26 of the first half-shell penetrate some millimeters into first chamber 30 of second half-shell 3. In this context, printed-circuit board 4 is pressed into gel layer 13 of second half-shell 3. Gel layers 12 and 13 are compressed and gel is squeezed out of the overlapping area. The compressed gel is partially pressed, between set-apart interior walls 25 and 35 and set-apart interior walls 26 and 36, into second chambers 27 a and 27 b of first half-shell 2. As a result of the partial penetration of first chamber 20 of first half-shell 2, filled with gel 12, into first chamber 30 of second half-shell 3, filled with gel 13, enough gel can be squeezed out to assure with sufficient certainty that the printed-circuit board, having its electrical connecting leads, is completely enveloped by gel, i.e., is encapsulated in gel. The quantity of displaced gel, in this context, can be adjusted through parameters a, b, and c.

[0023] When both half-shells 2, 3 are joined together, C-shaped cutouts 28, 38 form a circular opening for the feeding through of connecting lead 5. Conductors 15 of conducting lead 5 are brought into contact with connector 8 through the gap between interior walls 25 and 35, and are completely enveloped by gel. U-shaped cutouts 29, 39 of both half-shells 2, 3, in the joined state of the two half-shells 2, 3, form a slot-shaped opening, through which foil conductor 6 is conducted into second chambers 27 b, 37 b. From there, foil conductor 6 runs through the gap between interior walls 26 and 36 to printed-circuit board 4 and is enveloped on all sides by the gel that is present there.

[0024] When half-shells 2, 3 are joined together, detent hooks 44, inserted into openings 57, slide into guide slots 54, spring back behind projecting parts 55 in the guide slots, and finally, in a barbed manner, lock in, using their latches 45, behind projecting parts 55, as is depicted in FIG. 2. Width e of guide slot 54, in this context, is dimensioned so that assigned latch 45 can be conducted just barely between projecting part 55, extending into the guide slot, and the inner wall of the guide slot, opposite the projecting part. Advantageously, it can be provided that wall 59 of guide slot 54, provided with projecting part 55, in this context, is bent in an elastic manner and springs back as soon as latch 45 passes projecting part 55. It can advantageously be achieved, in this manner, that detent hooks 44 cannot be released from their latched position without being destroyed. The depicted latch connections make possible a reliable and stable latch connection of the two half-shells 2, 3.

[0025] The present invention is not limited to the exemplary embodiment depicted here. As is obvious, modifications of the design of the housing are possible. For example, the interior walls do not necessarily have to run parallel to each other. Thus it is conceivable, by way of example, to set off the first chamber in each half-shell, for example, by circular interior walls from a circular second chamber surrounding the first chamber, or similar modifications, it being important to remember that the interior walls of the second half-shell overlap the interior walls of the first half-shell with clearance, and the interior walls of the first half-shell penetrate somewhat into the first chamber of the second half-shell. In addition, of course, exemplary embodiments are also conceivable in which, in place of the foil conductor, a further connecting lead is used, or the control device having only one connecting lead. In place of the gel, another suitable fluid sealing material can be used, which, when the two half-shells are pressed together, is partially squeezed out. 

What is claimed is:
 1. An electrical device, comprising two housing parts (2, 3) that can be combined into one closed housing (1), the housing parts, in the joined state, enclosing a housing interior space, an electrical/electronic circuit element (4) arranged in the housing interior space, and a sealing material (12, 13) for protecting the circuit element (4), wherein the two housing parts (2, 3) are configured as half-shells, and the interior area of the half-shells (2, 3) is, in each case, subdivided by interior walls (25, 26, 35, 36) into at least two chambers (20, 27 a, 27 b, 30, 37 a, 37 b), of which, in each case, a first chamber (20, 30) is filled with the sealing material (12, 13) and has spatial dimensions that are larger than the dimensions of the circuit element (4), the interior walls (35, 36) of the second half-shell (3), in the joined state of the two half-shells (2, 3), overlapping with distance (d) the interior walls (25, 26) of the first half-shell (2), the interior walls (25, 26) of the first half-shell (2) penetrating a distance into the first chamber (30) of the second half-shell (3), and the circuit element (4) between the two half-shells (2, 3) being enveloped by the sealing material (12, 13) contained in the two first chambers (20, 30) up to its electrical connections (6, 15).
 2. The electrical device as recited in claim 1, wherein the interior area of the half-shells (2, 3), in each case, is subdivided by two interior walls (25, 26, 35, 36), running parallel to each other, which join with each other two side walls (22, 24, 32, 34), opposite each other, of the half-shells, into one centrally arranged first chamber (20, 30) and two second chambers (27 a, 27 b, 37 a, 37 b), laterally adjoining the first chamber.
 3. The electrical device as recited in claim 1 or 2, wherein, in each half-shell (2, 3), at least one second chamber (27 a, 27 b, 37 a, 37 b) is provided as a receiving area for excess sealing material that is squeezed out of the first chambers (20, 30) when the two half-shells are joined together, a discharge channel being formed by the distance (d) between the interior walls (25, 26, 35, 36) of the first and second half-shells, for sealing material that is squeezed out of the first chambers (20, 30).
 4. The electrical device as recited in claim 1, wherein the half-shells (2, 3) can be joined to each other by latching means (44, 54).
 5. The electrical device as recited in claim 4, wherein the latching means include detent hooks (44) arranged on one half-shell (2), the detent hooks engaging, in each case, in a guide slot (54), arranged on the other half-shell, and by their latches (45), in each case, grasping in barbed fashion a projecting part (55) arranged in the guide slot (54).
 6. The electrical device as recited in claim 5, wherein the width (e) of each guide slot and the geometrical dimensions of the corresponding latch (45) are adjusted to each other so that a latch (45), engaging, in a barbed manner, behind the projecting part (55), can no longer be released from its latched position without being destroyed.
 7. The electrical device as recited in claim 1, wherein the side walls (21, 31, 23, 33) of the half-shells (2, 3) have cutouts (28, 38, 29, 39), which, in the joined state of the housing part (1), form openings arranged between the two half-shells for the feeding through of the electrical connecting leads (5, 6).
 8. The electrical device as recited in claim 1, wherein, on at least one half-shell (3, 4), a strain relief device (42, 43) is provided for the electrical connecting leads (6).
 9. The electrical device as recited in one of the preceding claims, wherein the electrical connecting leads include an elastically flexible foil conductor (6).
 10. The electrical device as recited in claim 1, wherein as sealing material a gel is used. 